Reducing honey bee winter mortality with molybdenum supplementation: field evidence across Europe

Nutrition is key to improving honey bees' resilience to environmental
stress factors that threaten their health. Yet, little is known about the
micronutritional needs of colonies, in particular about molybdenum, an
essential trace element in biology. This study focuses on a coordination
complex based on molybdenum, Mo(+V), which was assessed for compatibility
with standard beekeeping practices. It was found to be non-toxic for bees,
stable, and easy to use. Importantly, it does not leave any residues in
the honey produced. This study investigated how supplementation with a few
milligrams of this complex can improve hive performance in early spring
and reduce winter mortality. Over a two-year field campaign, 283 beehives
spread over 6 apiaries located in Spain, Greece, and France were involved:
142 beehives supplemented with the molybdenum-based compound and 141
beehives as a control group. Supplementation resulted in a significant
reduction in winter colony losses, averaging a 44% decrease, ranging
between 27% and 75% in the different apiaries. The risk of death was twice
lower in the Na-Mo2O4-EDTA group compared to the control group (risk
ratio: 0.51). The impact on bee populations and honey production was also
evaluated. A significant increase in honey reserves within the brood area
of 107% was observed in the Greek apiary, whereas no comparable effect was
detected in Spain, suggesting that local environmental conditions or
management practices may influence this parameter. This study highlights
the importance of molybdenum in the management of honey bees as an
efficient tool to reduce the winter mortality of the colonies. The data
set provided on Dryad includes all raw data concerning the field test in
France, Spain, and Greece.